This three year project is designed to study the history of the changingg concept of fever as it was presented in published sources from the eighteenth to the twentieth centuries. The resulting monograph will trace the increasing definition of the various diseases which were all once called fever and will describe the effects of the change on the practice of medicine. Because of the great prevalence of febrile diseases in the period this study will provide an opportunity to illustrate, from the perspective of the unifying theme of concepts of fever, the many factors which influenced the emergence of modern medicine. These factors included the geographical and social distribution of diseases, and the role of societal and individual commitment to particular ideas both of the nature of disease and of social and economic organization as well as changes in scientific methods and the advancing knowledge of the basic sciences of biology and chemistry.